/*
 * Copyright © 2012 Red Hat
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice (including the next
 * paragraph) shall be included in all copies or substantial portions of the
 * Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
 * IN THE SOFTWARE.
 *
 * Authors:
 *      Dave Airlie <airlied@redhat.com>
 *      Rob Clark <rob.clark@linaro.org>
 *
 */

#include <linux/export.h>
#include <linux/dma-buf.h>
#include <linux/rbtree.h>

#include <drm/drm.h>
#include <drm/drm_drv.h>
#include <drm/drm_file.h>
#include <drm/drm_framebuffer.h>
#include <drm/drm_gem.h>
#include <drm/drm_prime.h>

#include "drm_internal.h"

/**
 * DOC: overview and lifetime rules
 *
 * Similar to GEM global names, PRIME file descriptors are also used to share
 * buffer objects across processes. They offer additional security: as file
 * descriptors must be explicitly sent over UNIX domain sockets to be shared
 * between applications, they can't be guessed like the globally unique GEM
 * names.
 *
 * Drivers that support the PRIME API implement the
 * &drm_driver.prime_handle_to_fd and &drm_driver.prime_fd_to_handle operations.
 * GEM based drivers must use drm_gem_prime_handle_to_fd() and
 * drm_gem_prime_fd_to_handle() to implement these. For GEM based drivers the
 * actual driver interfaces is provided through the &drm_gem_object_funcs.export
 * and &drm_driver.gem_prime_import hooks.
 *
 * &dma_buf_ops implementations for GEM drivers are all individually exported
 * for drivers which need to overwrite or reimplement some of them.
 *
 * Reference Counting for GEM Drivers
 * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 *
 * On the export the &dma_buf holds a reference to the exported buffer object,
 * usually a &drm_gem_object. It takes this reference in the PRIME_HANDLE_TO_FD
 * IOCTL, when it first calls &drm_gem_object_funcs.export
 * and stores the exporting GEM object in the &dma_buf.priv field. This
 * reference needs to be released when the final reference to the &dma_buf
 * itself is dropped and its &dma_buf_ops.release function is called.  For
 * GEM-based drivers, the &dma_buf should be exported using
 * drm_gem_dmabuf_export() and then released by drm_gem_dmabuf_release().
 *
 * Thus the chain of references always flows in one direction, avoiding loops:
 * importing GEM object -> dma-buf -> exported GEM bo. A further complication
 * are the lookup caches for import and export. These are required to guarantee
 * that any given object will always have only one uniqe userspace handle. This
 * is required to allow userspace to detect duplicated imports, since some GEM
 * drivers do fail command submissions if a given buffer object is listed more
 * than once. These import and export caches in &drm_prime_file_private only
 * retain a weak reference, which is cleaned up when the corresponding object is
 * released.
 *
 * Self-importing: If userspace is using PRIME as a replacement for flink then
 * it will get a fd->handle request for a GEM object that it created.  Drivers
 * should detect this situation and return back the underlying object from the
 * dma-buf private. For GEM based drivers this is handled in
 * drm_gem_prime_import() already.
 */

struct drm_prime_member {
    struct dma_buf *dma_buf;
    uint32_t handle;

    struct rb_node dmabuf_rb;
    struct rb_node handle_rb;
};

static int drm_prime_add_buf_handle(struct drm_prime_file_private *prime_fpriv, struct dma_buf *dma_buf,
                                    uint32_t handle)
{
    struct drm_prime_member *member;
    struct rb_node **p, *rb;

    member = kmalloc(sizeof(*member), GFP_KERNEL);
    if (!member) {
        return -ENOMEM;
    }

    get_dma_buf(dma_buf);
    member->dma_buf = dma_buf;
    member->handle = handle;

    rb = NULL;
    p = &prime_fpriv->dmabufs.rb_node;
    while (*p) {
        struct drm_prime_member *pos;

        rb = *p;
        pos = rb_entry(rb, struct drm_prime_member, dmabuf_rb);
        if (dma_buf > pos->dma_buf) {
            p = &rb->rb_right;
        } else {
            p = &rb->rb_left;
        }
    }
    rb_link_node(&member->dmabuf_rb, rb, p);
    rb_insert_color(&member->dmabuf_rb, &prime_fpriv->dmabufs);

    rb = NULL;
    p = &prime_fpriv->handles.rb_node;
    while (*p) {
        struct drm_prime_member *pos;

        rb = *p;
        pos = rb_entry(rb, struct drm_prime_member, handle_rb);
        if (handle > pos->handle) {
            p = &rb->rb_right;
        } else {
            p = &rb->rb_left;
        }
    }
    rb_link_node(&member->handle_rb, rb, p);
    rb_insert_color(&member->handle_rb, &prime_fpriv->handles);

    return 0;
}

static struct dma_buf *drm_prime_lookup_buf_by_handle(struct drm_prime_file_private *prime_fpriv, uint32_t handle)
{
    struct rb_node *rb;

    rb = prime_fpriv->handles.rb_node;
    while (rb) {
        struct drm_prime_member *member;

        member = rb_entry(rb, struct drm_prime_member, handle_rb);
        if (member->handle == handle) {
            return member->dma_buf;
        } else if (member->handle < handle) {
            rb = rb->rb_right;
        } else {
            rb = rb->rb_left;
        }
    }

    return NULL;
}

static int drm_prime_lookup_buf_handle(struct drm_prime_file_private *prime_fpriv, struct dma_buf *dma_buf,
                                       uint32_t *handle)
{
    struct rb_node *rb;

    rb = prime_fpriv->dmabufs.rb_node;
    while (rb) {
        struct drm_prime_member *member;

        member = rb_entry(rb, struct drm_prime_member, dmabuf_rb);
        if (member->dma_buf == dma_buf) {
            *handle = member->handle;
            return 0;
        } else if (member->dma_buf < dma_buf) {
            rb = rb->rb_right;
        } else {
            rb = rb->rb_left;
        }
    }

    return -ENOENT;
}

void drm_prime_remove_buf_handle_locked(struct drm_prime_file_private *prime_fpriv,
                    struct dma_buf *dma_buf)
{
    struct rb_node *rb;

    rb = prime_fpriv->dmabufs.rb_node;
    while (rb) {
        struct drm_prime_member *member;

        member = rb_entry(rb, struct drm_prime_member, dmabuf_rb);
        if (member->dma_buf == dma_buf) {
            rb_erase(&member->handle_rb, &prime_fpriv->handles);
            rb_erase(&member->dmabuf_rb, &prime_fpriv->dmabufs);

            dma_buf_put(dma_buf);
            kfree(member);
            return;
        } else if (member->dma_buf < dma_buf) {
            rb = rb->rb_right;
        } else {
            rb = rb->rb_left;
        }
    }
}

void drm_prime_init_file_private(struct drm_prime_file_private *prime_fpriv)
{
    mutex_init(&prime_fpriv->lock);
    prime_fpriv->dmabufs = RB_ROOT;
    prime_fpriv->handles = RB_ROOT;
}

void drm_prime_destroy_file_private(struct drm_prime_file_private *prime_fpriv)
{
    /* by now drm_gem_release should've made sure the list is empty */
    WARN_ON(!RB_EMPTY_ROOT(&prime_fpriv->dmabufs));
}

/**
 * drm_gem_dmabuf_export - &dma_buf export implementation for GEM
 * @dev: parent device for the exported dmabuf
 * @exp_info: the export information used by dma_buf_export()
 *
 * This wraps dma_buf_export() for use by generic GEM drivers that are using
 * drm_gem_dmabuf_release(). In addition to calling dma_buf_export(), we take
 * a reference to the &drm_device and the exported &drm_gem_object (stored in
 * &dma_buf_export_info.priv) which is released by drm_gem_dmabuf_release().
 *
 * Returns the new dmabuf.
 */
struct dma_buf *drm_gem_dmabuf_export(struct drm_device *dev, struct dma_buf_export_info *exp_info)
{
    struct drm_gem_object *obj = exp_info->priv;
    struct dma_buf *dma_buf;

    dma_buf = dma_buf_export(exp_info);
    if (IS_ERR(dma_buf)) {
        return dma_buf;
    }

    drm_dev_get(dev);
    drm_gem_object_get(obj);
    dma_buf->file->f_mapping = obj->dev->anon_inode->i_mapping;

    return dma_buf;
}
EXPORT_SYMBOL(drm_gem_dmabuf_export);

/**
 * drm_gem_dmabuf_release - &dma_buf release implementation for GEM
 * @dma_buf: buffer to be released
 *
 * Generic release function for dma_bufs exported as PRIME buffers. GEM drivers
 * must use this in their &dma_buf_ops structure as the release callback.
 * drm_gem_dmabuf_release() should be used in conjunction with
 * drm_gem_dmabuf_export().
 */
void drm_gem_dmabuf_release(struct dma_buf *dma_buf)
{
    struct drm_gem_object *obj = dma_buf->priv;
    struct drm_device *dev = obj->dev;

    /* drop the reference on the export fd holds */
    drm_gem_object_put(obj);

    drm_dev_put(dev);
}
EXPORT_SYMBOL(drm_gem_dmabuf_release);

/**
 * drm_gem_prime_fd_to_handle - PRIME import function for GEM drivers
 * @dev: dev to export the buffer from
 * @file_priv: drm file-private structure
 * @prime_fd: fd id of the dma-buf which should be imported
 * @handle: pointer to storage for the handle of the imported buffer object
 *
 * This is the PRIME import function which must be used mandatorily by GEM
 * drivers to ensure correct lifetime management of the underlying GEM object.
 * The actual importing of GEM object from the dma-buf is done through the
 * &drm_driver.gem_prime_import driver callback.
 *
 * Returns 0 on success or a negative error code on failure.
 */
int drm_gem_prime_fd_to_handle(struct drm_device *dev, struct drm_file *file_priv, int prime_fd, uint32_t *handle)
{
    struct dma_buf *dma_buf;
    struct drm_gem_object *obj;
    int ret;

    dma_buf = dma_buf_get(prime_fd);
    if (IS_ERR(dma_buf)) {
        return PTR_ERR(dma_buf);
    }

    mutex_lock(&file_priv->prime.lock);

    ret = drm_prime_lookup_buf_handle(&file_priv->prime, dma_buf, handle);
    if (ret == 0) {
        goto out_put;
    }

    /* never seen this one, need to import */
    mutex_lock(&dev->object_name_lock);
    if (dev->driver->gem_prime_import) {
        obj = dev->driver->gem_prime_import(dev, dma_buf);
    } else {
        obj = drm_gem_prime_import(dev, dma_buf);
    }
    if (IS_ERR(obj)) {
        ret = PTR_ERR(obj);
        goto out_unlock;
    }

    if (obj->dma_buf) {
        WARN_ON(obj->dma_buf != dma_buf);
    } else {
        obj->dma_buf = dma_buf;
        get_dma_buf(dma_buf);
    }

    /* _handle_create_tail unconditionally unlocks dev->object_name_lock. */
    ret = drm_gem_handle_create_tail(file_priv, obj, handle);
    drm_gem_object_put(obj);
    if (ret) {
        goto out_put;
    }

    ret = drm_prime_add_buf_handle(&file_priv->prime, dma_buf, *handle);
    mutex_unlock(&file_priv->prime.lock);
    if (ret) {
        goto fail;
    }

    dma_buf_put(dma_buf);

    return 0;

fail:
    /* hmm, if driver attached, we are relying on the free-object path
     * to detach.. which seems ok..
     */
    drm_gem_handle_delete(file_priv, *handle);
    dma_buf_put(dma_buf);
    return ret;

out_unlock:
    mutex_unlock(&dev->object_name_lock);
out_put:
    mutex_unlock(&file_priv->prime.lock);
    dma_buf_put(dma_buf);
    return ret;
}
EXPORT_SYMBOL(drm_gem_prime_fd_to_handle);

int drm_prime_fd_to_handle_ioctl(struct drm_device *dev, void *data, struct drm_file *file_priv)
{
    struct drm_prime_handle *args = data;

    if (!dev->driver->prime_fd_to_handle) {
        return -ENOSYS;
    }

    return dev->driver->prime_fd_to_handle(dev, file_priv, args->fd, &args->handle);
}

static struct dma_buf *export_and_register_object(struct drm_device *dev, struct drm_gem_object *obj, uint32_t flags)
{
    struct dma_buf *dmabuf;

    /* prevent races with concurrent gem_close. */
    if (obj->handle_count == 0) {
        dmabuf = ERR_PTR(-ENOENT);
        return dmabuf;
    }

    if (obj->funcs && obj->funcs->export) {
        dmabuf = obj->funcs->export(obj, flags);
    } else if (dev->driver->gem_prime_export) {
        dmabuf = dev->driver->gem_prime_export(obj, flags);
    } else {
        dmabuf = drm_gem_prime_export(obj, flags);
    }
    if (IS_ERR(dmabuf)) {
        /* normally the created dma-buf takes ownership of the ref,
         * but if that fails then drop the ref
         */
        return dmabuf;
    }

    /*
     * Note that callers do not need to clean up the export cache
     * since the check for obj->handle_count guarantees that someone
     * will clean it up.
     */
    obj->dma_buf = dmabuf;
    get_dma_buf(obj->dma_buf);

    return dmabuf;
}

/**
 * drm_gem_prime_handle_to_fd - PRIME export function for GEM drivers
 * @dev: dev to export the buffer from
 * @file_priv: drm file-private structure
 * @handle: buffer handle to export
 * @flags: flags like DRM_CLOEXEC
 * @prime_fd: pointer to storage for the fd id of the create dma-buf
 *
 * This is the PRIME export function which must be used mandatorily by GEM
 * drivers to ensure correct lifetime management of the underlying GEM object.
 * The actual exporting from GEM object to a dma-buf is done through the
 * &drm_driver.gem_prime_export driver callback.
 */
int drm_gem_prime_handle_to_fd(struct drm_device *dev, struct drm_file *file_priv, uint32_t handle, uint32_t flags,
                               int *prime_fd)
{
    struct drm_gem_object *obj;
    int ret = 0;
    struct dma_buf *dmabuf;

    mutex_lock(&file_priv->prime.lock);
    obj = drm_gem_object_lookup(file_priv, handle);
    if (!obj) {
        ret = -ENOENT;
        goto out_unlock;
    }

    dmabuf = drm_prime_lookup_buf_by_handle(&file_priv->prime, handle);
    if (dmabuf) {
        get_dma_buf(dmabuf);
        goto out_have_handle;
    }

    mutex_lock(&dev->object_name_lock);
    /* re-export the original imported object */
    if (obj->import_attach) {
        dmabuf = obj->import_attach->dmabuf;
        get_dma_buf(dmabuf);
        goto out_have_obj;
    }

    if (obj->dma_buf) {
        get_dma_buf(obj->dma_buf);
        dmabuf = obj->dma_buf;
        goto out_have_obj;
    }

    dmabuf = export_and_register_object(dev, obj, flags);
    if (IS_ERR(dmabuf)) {
        /* normally the created dma-buf takes ownership of the ref,
         * but if that fails then drop the ref
         */
        ret = PTR_ERR(dmabuf);
        mutex_unlock(&dev->object_name_lock);
        goto out;
    }

out_have_obj:
    /*
     * If we've exported this buffer then cheat and add it to the import list
     * so we get the correct handle back. We must do this under the
     * protection of dev->object_name_lock to ensure that a racing gem close
     * ioctl doesn't miss to remove this buffer handle from the cache.
     */
    ret = drm_prime_add_buf_handle(&file_priv->prime, dmabuf, handle);
    mutex_unlock(&dev->object_name_lock);
    if (ret) {
        goto fail_put_dmabuf;
    }

out_have_handle:
    ret = dma_buf_fd(dmabuf, flags);
    /*
     * We must _not_ remove the buffer from the handle cache since the newly
     * created dma buf is already linked in the global obj->dma_buf pointer,
     * and that is invariant as long as a userspace gem handle exists.
     * Closing the handle will clean out the cache anyway, so we don't leak.
     */
    if (ret < 0) {
        goto fail_put_dmabuf;
    } else {
        *prime_fd = ret;
        ret = 0;
    }

    goto out;

fail_put_dmabuf:
    dma_buf_put(dmabuf);
out:
    drm_gem_object_put(obj);
out_unlock:
    mutex_unlock(&file_priv->prime.lock);

    return ret;
}
EXPORT_SYMBOL(drm_gem_prime_handle_to_fd);

int drm_prime_handle_to_fd_ioctl(struct drm_device *dev, void *data, struct drm_file *file_priv)
{
    struct drm_prime_handle *args = data;

    if (!dev->driver->prime_handle_to_fd) {
        return -ENOSYS;
    }

    /* check flags are valid */
    if (args->flags & ~(DRM_CLOEXEC | DRM_RDWR)) {
        return -EINVAL;
    }

    return dev->driver->prime_handle_to_fd(dev, file_priv, args->handle, args->flags, &args->fd);
}

/**
 * DOC: PRIME Helpers
 *
 * Drivers can implement &drm_gem_object_funcs.export and
 * &drm_driver.gem_prime_import in terms of simpler APIs by using the helper
 * functions drm_gem_prime_export() and drm_gem_prime_import(). These functions
 * implement dma-buf support in terms of some lower-level helpers, which are
 * again exported for drivers to use individually:
 *
 * Exporting buffers
 * ~~~~~~~~~~~~~~~~~
 *
 * Optional pinning of buffers is handled at dma-buf attach and detach time in
 * drm_gem_map_attach() and drm_gem_map_detach(). Backing storage itself is
 * handled by drm_gem_map_dma_buf() and drm_gem_unmap_dma_buf(), which relies on
 * &drm_gem_object_funcs.get_sg_table.
 *
 * For kernel-internal access there's drm_gem_dmabuf_vmap() and
 * drm_gem_dmabuf_vunmap(). Userspace mmap support is provided by
 * drm_gem_dmabuf_mmap().
 *
 * Note that these export helpers can only be used if the underlying backing
 * storage is fully coherent and either permanently pinned, or it is safe to pin
 * it indefinitely.
 *
 * The underlying helper functions are named rather inconsistently.
 *
 * Exporting buffers
 * ~~~~~~~~~~~~~~~~~
 *
 * Importing dma-bufs using drm_gem_prime_import() relies on
 * &drm_driver.gem_prime_import_sg_table.
 *
 * Note that similarly to the export helpers this permanently pins the
 * underlying backing storage. Which is ok for scanout, but is not the best
 * option for sharing lots of buffers for rendering.
 */

/**
 * drm_gem_map_attach - dma_buf attach implementation for GEM
 * @dma_buf: buffer to attach device to
 * @attach: buffer attachment data
 *
 * Calls &drm_gem_object_funcs.pin for device specific handling. This can be
 * used as the &dma_buf_ops.attach callback. Must be used together with
 * drm_gem_map_detach().
 *
 * Returns 0 on success, negative error code on failure.
 */
int drm_gem_map_attach(struct dma_buf *dma_buf, struct dma_buf_attachment *attach)
{
    struct drm_gem_object *obj = dma_buf->priv;

    return drm_gem_pin(obj);
}
EXPORT_SYMBOL(drm_gem_map_attach);

/**
 * drm_gem_map_detach - dma_buf detach implementation for GEM
 * @dma_buf: buffer to detach from
 * @attach: attachment to be detached
 *
 * Calls &drm_gem_object_funcs.pin for device specific handling.  Cleans up
 * &dma_buf_attachment from drm_gem_map_attach(). This can be used as the
 * &dma_buf_ops.detach callback.
 */
void drm_gem_map_detach(struct dma_buf *dma_buf, struct dma_buf_attachment *attach)
{
    struct drm_gem_object *obj = dma_buf->priv;

    drm_gem_unpin(obj);
}
EXPORT_SYMBOL(drm_gem_map_detach);

/**
 * drm_gem_map_dma_buf - map_dma_buf implementation for GEM
 * @attach: attachment whose scatterlist is to be returned
 * @dir: direction of DMA transfer
 *
 * Calls &drm_gem_object_funcs.get_sg_table and then maps the scatterlist. This
 * can be used as the &dma_buf_ops.map_dma_buf callback. Should be used together
 * with drm_gem_unmap_dma_buf().
 *
 * Returns:sg_table containing the scatterlist to be returned; returns ERR_PTR
 * on error. May return -EINTR if it is interrupted by a signal.
 */
struct sg_table *drm_gem_map_dma_buf(struct dma_buf_attachment *attach, enum dma_data_direction dir)
{
    struct drm_gem_object *obj = attach->dmabuf->priv;
    struct sg_table *sgt;
    int ret;

    if (WARN_ON(dir == DMA_NONE)) {
        return ERR_PTR(-EINVAL);
    }

    if (obj->funcs) {
        sgt = obj->funcs->get_sg_table(obj);
    } else {
        sgt = obj->dev->driver->gem_prime_get_sg_table(obj);
    }

    ret = dma_map_sgtable(attach->dev, sgt, dir, DMA_ATTR_SKIP_CPU_SYNC);
    if (ret) {
        sg_free_table(sgt);
        kfree(sgt);
        sgt = ERR_PTR(ret);
    }

    return sgt;
}
EXPORT_SYMBOL(drm_gem_map_dma_buf);

/**
 * drm_gem_unmap_dma_buf - unmap_dma_buf implementation for GEM
 * @attach: attachment to unmap buffer from
 * @sgt: scatterlist info of the buffer to unmap
 * @dir: direction of DMA transfer
 *
 * This can be used as the &dma_buf_ops.unmap_dma_buf callback.
 */
void drm_gem_unmap_dma_buf(struct dma_buf_attachment *attach, struct sg_table *sgt, enum dma_data_direction dir)
{
    if (!sgt) {
        return;
    }

    dma_unmap_sgtable(attach->dev, sgt, dir, DMA_ATTR_SKIP_CPU_SYNC);
    sg_free_table(sgt);
    kfree(sgt);
}
EXPORT_SYMBOL(drm_gem_unmap_dma_buf);

/**
 * drm_gem_dmabuf_vmap - dma_buf vmap implementation for GEM
 * @dma_buf: buffer to be mapped
 *
 * Sets up a kernel virtual mapping. This can be used as the &dma_buf_ops.vmap
 * callback. Calls into &drm_gem_object_funcs.vmap for device specific handling.
 *
 * Returns the kernel virtual address or NULL on failure.
 */
void *drm_gem_dmabuf_vmap(struct dma_buf *dma_buf)
{
    struct drm_gem_object *obj = dma_buf->priv;
    void *vaddr;

    vaddr = drm_gem_vmap(obj);
    if (IS_ERR(vaddr)) {
        vaddr = NULL;
    }

    return vaddr;
}
EXPORT_SYMBOL(drm_gem_dmabuf_vmap);

/**
 * drm_gem_dmabuf_vunmap - dma_buf vunmap implementation for GEM
 * @dma_buf: buffer to be unmapped
 * @vaddr: the virtual address of the buffer
 *
 * Releases a kernel virtual mapping. This can be used as the
 * &dma_buf_ops.vunmap callback. Calls into &drm_gem_object_funcs.vunmap for device specific handling.
 */
void drm_gem_dmabuf_vunmap(struct dma_buf *dma_buf, void *vaddr)
{
    struct drm_gem_object *obj = dma_buf->priv;

    drm_gem_vunmap(obj, vaddr);
}
EXPORT_SYMBOL(drm_gem_dmabuf_vunmap);

/**
 * drm_gem_prime_mmap - PRIME mmap function for GEM drivers
 * @obj: GEM object
 * @vma: Virtual address range
 *
 * This function sets up a userspace mapping for PRIME exported buffers using
 * the same codepath that is used for regular GEM buffer mapping on the DRM fd.
 * The fake GEM offset is added to vma->vm_pgoff and &drm_driver->fops->mmap is
 * called to set up the mapping.
 *
 * Drivers can use this as their &drm_driver.gem_prime_mmap callback.
 */
int drm_gem_prime_mmap(struct drm_gem_object *obj, struct vm_area_struct *vma)
{
    struct drm_file *priv;
    struct file *fil;
    int ret;

    /* Add the fake offset */
    vma->vm_pgoff += drm_vma_node_start(&obj->vma_node);

    if (obj->funcs && obj->funcs->mmap) {
        ret = obj->funcs->mmap(obj, vma);
        if (ret) {
            return ret;
        }
        vma->vm_private_data = obj;
        drm_gem_object_get(obj);
        return 0;
    }

    priv = kzalloc(sizeof(*priv), GFP_KERNEL);
    fil = kzalloc(sizeof(*fil), GFP_KERNEL);
    if (!priv || !fil) {
        ret = -ENOMEM;
        goto out;
    }

    /* Used by drm_gem_mmap() to lookup the GEM object */
    priv->minor = obj->dev->primary;
    fil->private_data = priv;

    ret = drm_vma_node_allow(&obj->vma_node, priv);
    if (ret) {
        goto out;
    }

    ret = obj->dev->driver->fops->mmap(fil, vma);

    drm_vma_node_revoke(&obj->vma_node, priv);
out:
    kfree(priv);
    kfree(fil);

    return ret;
}
EXPORT_SYMBOL(drm_gem_prime_mmap);

/**
 * drm_gem_dmabuf_mmap - dma_buf mmap implementation for GEM
 * @dma_buf: buffer to be mapped
 * @vma: virtual address range
 *
 * Provides memory mapping for the buffer. This can be used as the
 * &dma_buf_ops.mmap callback. It just forwards to &drm_driver.gem_prime_mmap,
 * which should be set to drm_gem_prime_mmap().
 *
 * There's really no point to this wrapper, drivers which need anything
 * else but drm_gem_prime_mmap can roll their own &dma_buf_ops.mmap callback.
 *
 * Returns 0 on success or a negative error code on failure.
 */
int drm_gem_dmabuf_mmap(struct dma_buf *dma_buf, struct vm_area_struct *vma)
{
    struct drm_gem_object *obj = dma_buf->priv;
    struct drm_device *dev = obj->dev;

    if (!dev->driver->gem_prime_mmap) {
        return -ENOSYS;
    }

    return dev->driver->gem_prime_mmap(obj, vma);
}
EXPORT_SYMBOL(drm_gem_dmabuf_mmap);

/**
 * drm_gem_dmabuf_get_uuid - dma_buf get_uuid implementation for GEM
 * @dma_buf: buffer to query
 * @uuid: uuid outparam
 *
 * Queries the buffer's virtio UUID. This can be used as the
 * &dma_buf_ops.get_uuid callback. Calls into &drm_driver.gem_prime_get_uuid.
 *
 * Returns 0 on success or a negative error code on failure.
 */
int drm_gem_dmabuf_get_uuid(struct dma_buf *dma_buf, uuid_t *uuid)
{
    struct drm_gem_object *obj = dma_buf->priv;
    struct drm_device *dev = obj->dev;

    if (!dev->driver->gem_prime_get_uuid) {
        return -ENODEV;
    }

    return dev->driver->gem_prime_get_uuid(obj, uuid);
}
EXPORT_SYMBOL(drm_gem_dmabuf_get_uuid);

static const struct dma_buf_ops drm_gem_prime_dmabuf_ops = {
    .cache_sgt_mapping = true,
    .attach = drm_gem_map_attach,
    .detach = drm_gem_map_detach,
    .map_dma_buf = drm_gem_map_dma_buf,
    .unmap_dma_buf = drm_gem_unmap_dma_buf,
    .release = drm_gem_dmabuf_release,
    .mmap = drm_gem_dmabuf_mmap,
    .vmap = drm_gem_dmabuf_vmap,
    .vunmap = drm_gem_dmabuf_vunmap,
    .get_uuid = drm_gem_dmabuf_get_uuid,
};

/**
 * drm_prime_pages_to_sg - converts a page array into an sg list
 * @dev: DRM device
 * @pages: pointer to the array of page pointers to convert
 * @nr_pages: length of the page vector
 *
 * This helper creates an sg table object from a set of pages
 * the driver is responsible for mapping the pages into the
 * importers address space for use with dma_buf itself.
 *
 * This is useful for implementing &drm_gem_object_funcs.get_sg_table.
 */
struct sg_table *drm_prime_pages_to_sg(struct drm_device *dev, struct page **pages, unsigned int nr_pages)
{
    struct sg_table *sg;
    struct scatterlist *sge;
    size_t max_segment = 0;

    sg = kmalloc(sizeof(struct sg_table), GFP_KERNEL);
    if (!sg) {
        return ERR_PTR(-ENOMEM);
    }

    if (dev) {
        max_segment = dma_max_mapping_size(dev->dev);
    }
    if (max_segment == 0 || max_segment > SCATTERLIST_MAX_SEGMENT) {
        max_segment = SCATTERLIST_MAX_SEGMENT;
    }
    sge = __sg_alloc_table_from_pages(sg, pages, nr_pages, 0, nr_pages << PAGE_SHIFT, max_segment, NULL, 0, GFP_KERNEL);
    if (IS_ERR(sge)) {
        kfree(sg);
        sg = ERR_CAST(sge);
    }
    return sg;
}
EXPORT_SYMBOL(drm_prime_pages_to_sg);

/**
 * drm_prime_get_contiguous_size - returns the contiguous size of the buffer
 * @sgt: sg_table describing the buffer to check
 *
 * This helper calculates the contiguous size in the DMA address space
 * of the the buffer described by the provided sg_table.
 *
 * This is useful for implementing
 * &drm_gem_object_funcs.gem_prime_import_sg_table.
 */
unsigned long drm_prime_get_contiguous_size(struct sg_table *sgt)
{
    dma_addr_t expected = sg_dma_address(sgt->sgl);
    struct scatterlist *sg;
    unsigned long size = 0;
    int i;

    for_each_sgtable_dma_sg(sgt, sg, i)
    {
        unsigned int len = sg_dma_len(sg);
        if (!len) {
            break;
        }
        if (sg_dma_address(sg) != expected) {
            break;
        }
        expected += len;
        size += len;
    }
    return size;
}
EXPORT_SYMBOL(drm_prime_get_contiguous_size);

/**
 * drm_gem_prime_export - helper library implementation of the export callback
 * @obj: GEM object to export
 * @flags: flags like DRM_CLOEXEC and DRM_RDWR
 *
 * This is the implementation of the &drm_gem_object_funcs.export functions for GEM drivers
 * using the PRIME helpers. It is used as the default in
 * drm_gem_prime_handle_to_fd().
 */
struct dma_buf *drm_gem_prime_export(struct drm_gem_object *obj, int flags)
{
    struct drm_device *dev = obj->dev;
    struct dma_buf_export_info exp_info = {
        .exp_name = KBUILD_MODNAME, /* white lie for debug */
        .owner = dev->driver->fops->owner,
        .ops = &drm_gem_prime_dmabuf_ops,
        .size = obj->size,
        .flags = flags,
        .priv = obj,
        .resv = obj->resv,
    };

    return drm_gem_dmabuf_export(dev, &exp_info);
}
EXPORT_SYMBOL(drm_gem_prime_export);

/**
 * drm_gem_prime_import_dev - core implementation of the import callback
 * @dev: drm_device to import into
 * @dma_buf: dma-buf object to import
 * @attach_dev: struct device to dma_buf attach
 *
 * This is the core of drm_gem_prime_import(). It's designed to be called by
 * drivers who want to use a different device structure than &drm_device.dev for
 * attaching via dma_buf. This function calls
 * &drm_driver.gem_prime_import_sg_table internally.
 *
 * Drivers must arrange to call drm_prime_gem_destroy() from their
 * &drm_gem_object_funcs.free hook when using this function.
 */
struct drm_gem_object *drm_gem_prime_import_dev(struct drm_device *dev, struct dma_buf *dma_buf,
                                                struct device *attach_dev)
{
    struct dma_buf_attachment *attach;
    struct sg_table *sgt;
    struct drm_gem_object *obj;
    int ret;

    if (dma_buf->ops == &drm_gem_prime_dmabuf_ops) {
        obj = dma_buf->priv;
        if (obj->dev == dev) {
            /*
             * Importing dmabuf exported from out own gem increases
             * refcount on gem itself instead of f_count of dmabuf.
             */
            drm_gem_object_get(obj);
            return obj;
        }
    }

    if (!dev->driver->gem_prime_import_sg_table) {
        return ERR_PTR(-EINVAL);
    }

    attach = dma_buf_attach(dma_buf, attach_dev);
    if (IS_ERR(attach)) {
        return ERR_CAST(attach);
    }

    get_dma_buf(dma_buf);

    sgt = dma_buf_map_attachment(attach, DMA_BIDIRECTIONAL);
    if (IS_ERR(sgt)) {
        ret = PTR_ERR(sgt);
        goto fail_detach;
    }

    obj = dev->driver->gem_prime_import_sg_table(dev, attach, sgt);
    if (IS_ERR(obj)) {
        ret = PTR_ERR(obj);
        goto fail_unmap;
    }

    obj->import_attach = attach;
    obj->resv = dma_buf->resv;

    return obj;

fail_unmap:
    dma_buf_unmap_attachment(attach, sgt, DMA_BIDIRECTIONAL);
fail_detach:
    dma_buf_detach(dma_buf, attach);
    dma_buf_put(dma_buf);

    return ERR_PTR(ret);
}
EXPORT_SYMBOL(drm_gem_prime_import_dev);

/**
 * drm_gem_prime_import - helper library implementation of the import callback
 * @dev: drm_device to import into
 * @dma_buf: dma-buf object to import
 *
 * This is the implementation of the gem_prime_import functions for GEM drivers
 * using the PRIME helpers. Drivers can use this as their
 * &drm_driver.gem_prime_import implementation. It is used as the default
 * implementation in drm_gem_prime_fd_to_handle().
 *
 * Drivers must arrange to call drm_prime_gem_destroy() from their
 * &drm_gem_object_funcs.free hook when using this function.
 */
struct drm_gem_object *drm_gem_prime_import(struct drm_device *dev, struct dma_buf *dma_buf)
{
    return drm_gem_prime_import_dev(dev, dma_buf, dev->dev);
}
EXPORT_SYMBOL(drm_gem_prime_import);

/**
 * drm_prime_sg_to_page_addr_arrays - convert an sg table into a page array
 * @sgt: scatter-gather table to convert
 * @pages: optional array of page pointers to store the page array in
 * @addrs: optional array to store the dma bus address of each page
 * @max_entries: size of both the passed-in arrays
 *
 * Exports an sg table into an array of pages and addresses. This is currently
 * required by the TTM driver in order to do correct fault handling.
 *
 * Drivers can use this in their &drm_driver.gem_prime_import_sg_table
 * implementation.
 */
int drm_prime_sg_to_page_addr_arrays(struct sg_table *sgt, struct page **pages, dma_addr_t *addrs, int max_entries)
{
    struct sg_dma_page_iter dma_iter;
    struct sg_page_iter page_iter;
    struct page **p = pages;
    dma_addr_t *a = addrs;

    if (pages) {
        for_each_sgtable_page(sgt, &page_iter, 0)
        {
            if (WARN_ON(p - pages >= max_entries)) {
                return -1;
            }
            *p++ = sg_page_iter_page(&page_iter);
        }
    }
    if (addrs) {
        for_each_sgtable_dma_page(sgt, &dma_iter, 0)
        {
            if (WARN_ON(a - addrs >= max_entries)) {
                return -1;
            }
            *a++ = sg_page_iter_dma_address(&dma_iter);
        }
    }

    return 0;
}
EXPORT_SYMBOL(drm_prime_sg_to_page_addr_arrays);

/**
 * drm_prime_gem_destroy - helper to clean up a PRIME-imported GEM object
 * @obj: GEM object which was created from a dma-buf
 * @sg: the sg-table which was pinned at import time
 *
 * This is the cleanup functions which GEM drivers need to call when they use
 * drm_gem_prime_import() or drm_gem_prime_import_dev() to import dma-bufs.
 */
void drm_prime_gem_destroy(struct drm_gem_object *obj, struct sg_table *sg)
{
    struct dma_buf_attachment *attach;
    struct dma_buf *dma_buf;

    attach = obj->import_attach;
    if (sg) {
        dma_buf_unmap_attachment(attach, sg, DMA_BIDIRECTIONAL);
    }
    dma_buf = attach->dmabuf;
    dma_buf_detach(attach->dmabuf, attach);
    /* remove the reference */
    dma_buf_put(dma_buf);
}
EXPORT_SYMBOL(drm_prime_gem_destroy);
